Dependence of modelled evacuation times on key parameters and interactions

Abstract

Times and patterns of buildings evacuations involve interactions between many behavioral parameters reflected in the increasing complexity of computer simulations. A combination of detailed GridFlow computer evacuations simulations, calculation models and experimental evacuations have been used to determine the extent to which evacuation patterns and times are largely dependent upon a small number of key parameters and interactions. Cases investigated included a single retail enclosure and multi-enclosure, multi-storey office buildings designed following UK prescriptive guidance. It is concluded that evacuation times are very dependent upon a small number of critical factors (including pre travel activity time [PTAT] distributions, exit choice ratios, maximum flow rates, merge ratios, and densities of stationary and moving groups). Even sophisticated computer simulations can give misleading results if these factors are not adequately represented.. while simple calculation methods can provide a useful first estimate of evacuation times for designers, and a useful check on the performance of more complex simulation models.

Transparency vs magic numbers: The development of stair design requirements in the Italian Fire Safety Code

“…In order to assess the capacity of stairs during the vertical egress, a maximum population density in the stairs needs to be assumed. The assumed capacity is chosen in line with the maximum densities achieved in a set of experiments conducted in the UK [29] and compatible with data for the able-bodied population from evacuation drills recorded by the National Standards of Institute and Technology (NIST) in the USA [30] and VTT in Finland [31]. A summary of the assumptions employed is presented in Table 1.…”

Real-time Stochastic Evacuation Models for Decision Support in Actual Emergencies

“…Therefore, they should concentrate in the most essential parameters and interactions and ignores the less essential ones. The proposed models are based on the idea that evacuation calculations can be performed by addressing a small set of random parameters that have impact in the outcomes [21]. For the analysis of evacuation process in passenger trains, we suggest that the dominant parameters are the time spent to prepare for evacuation and the flow through the available exits.…”

Experimental studies to investigate merging behaviour in a staircase

“…Spreadsheet modelling calculations by Purser and Utting 3 have predicted that, for buildings designed for simultaneous evacuation according to prescriptive guidance, the rates of floor clearance halve at each successively higher floor if merge ratios of approximately 50:50 occur once the stair becomes congested, and that this could potentially lead to floor clearance times significantly greater than the 2.5 min target flow time on upper floors. The quantification of merging flows and the factors that influence merging behaviour are important considerations in our understanding of building evacuation, particularly high‐rise building evacuation, optimizing escape route design and essential for evacuation modelling 4–7. To date, a limited number of studies have specifically investigated the nature of merging flows.…”